I've scanned in a bunch of old family pictures, and the back of the photos has a description of what's in them. How can I take the 2 .jpg files from the scanned and butt them together, side to side into a single image?
Just open them, drag the one from the Layers Panel over to the other’s window or use copy/paste if you prefer or use File > Place to place an unopened image in the open one, enlarge the canvas of the receiving image (Edit > Canvas Size) and manually arrange them.
But if there is a large number of images you may want to look into automating the process.
Actions may provide a starting point.